/*
 * InspIRCd -- Internet Relay Chat Daemon
 *
 *   Copyright (C) 2018, 2020-2021 Sadie Powell <sadie@witchery.services>
 *   Copyright (C) 2014, 2016, 2018 Attila Molnar <attilamolnar@hush.com>
 *
 * This file is part of InspIRCd.  InspIRCd is free software: you can
 * redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation, version 2.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */


#pragma once

namespace stdalgo
{
	namespace vector
	{
		/**
		 * Erase a single element from a vector by overwriting it with a copy of the last element,
		 * which is then removed. This, in contrast to vector::erase(), does not result in all
		 * elements after the erased element being moved.
		 * Returns nothing, but all iterators, references and pointers to the erased element and the
		 * last element are invalidated
		 * @param vect Vector to remove the element from
		 * @param it Iterator to the element to remove
		 */
		template <typename T>
		inline void swaperase(typename std::vector<T>& vect, const typename std::vector<T>::iterator& it)
		{
			*it = vect.back();
			vect.pop_back();
		}

		/**
		 * Find and if exists, erase a single element from a vector by overwriting it with a
		 * copy of the last element, which is then removed. This, in contrast to vector::erase(),
		 * does not result in all elements after the erased element being moved.
		 * If the given value occurs multiple times, the one with the lowest index is removed.
		 * Individual elements are compared to the given value using operator==().
		 * @param vect Vector to remove the element from
		 * @param val Value of the element to look for and remove
		 * @return True if the element was found and removed, false if it wasn't found.
		 * If true, all iterators, references and pointers pointing to either the first element that
		 * is equal to val or to the last element are invalidated.
		 */
		template <typename T>
		inline bool swaperase(typename std::vector<T>& vect, const T& val)
		{
			const typename std::vector<T>::iterator it = std::find(vect.begin(), vect.end(), val);
			if (it != vect.end())
			{
				swaperase(vect, it);
				return true;
			}
			return false;
		}
	}

	namespace string
	{
		/** Get underlying C string of the string passed as parameter. Useful in template functions.
		 * @param str C string
		 * @return Same as input
		 */
		inline const char* tocstr(const char* str)
		{
			return str;
		}

		/** Get underlying C string of the string passed as parameter. Useful in template functions.
		 * @param str std::string object
		 * @return str.c_str()
		 */
		inline const char* tocstr(const std::string& str)
		{
			return str.c_str();
		}

		/** Check if two strings are equal case insensitively.
		 * @param str1 First string to compare.
		 * @param str2 Second string to compare.
		 * @return True if the strings are equal case-insensitively, false otherwise.
		 */
		template <typename S1, typename S2>
		inline bool equalsci(const S1& str1, const S2& str2)
		{
			return (!strcasecmp(tocstr(str1), tocstr(str2)));
		}

		/** Joins the contents of a vector to a string.
		 * @param sequence Zero or more items to join.
		 * @param separator The character to place between the items, defaults to ' ' (space).
		 * @return The joined string.
		 */
		template<typename Collection>
		inline std::string join(const Collection& sequence, char separator = ' ')
		{
			std::string joined;
			if (sequence.empty())
				return joined;

			for (const auto& element : sequence)
				joined.append(ConvToStr(element)).push_back(separator);

			joined.erase(joined.end() - 1);
			return joined;
		}

		/** Replace first occurrence of a substring ('target') in a string ('str') with another string ('replacement').
		 * @param str String to perform replacement in
		 * @param target String to replace
		 * @param replacement String to put in place of 'target'
		 * @return True if 'target' was replaced with 'replacement', false if it was not found in 'str'.
		 */
		template<typename CharT, typename Traits, typename Alloc>
		inline bool replace(std::basic_string<CharT, Traits, Alloc>& str, const std::basic_string<CharT, Traits, Alloc>& target, const std::basic_string<CharT, Traits, Alloc>& replacement)
		{
			const typename std::basic_string<CharT, Traits, Alloc>::size_type p = str.find(target);
			if (p == std::basic_string<CharT, Traits, Alloc>::npos)
				return false;
			str.replace(p, target.size(), replacement);
			return true;
		}

		/** Replace all occurrences of a string ('target') in a string ('str') with another string ('replacement').
		 * @param str String to perform replacement in
		 * @param target String to replace
		 * @param replacement String to put in place of 'target'
		 */
		template<typename CharT, typename Traits, typename Alloc>
		inline void replace_all(std::basic_string<CharT, Traits, Alloc>& str, const std::basic_string<CharT, Traits, Alloc>& target, const std::basic_string<CharT, Traits, Alloc>& replacement)
		{
			if (target.empty())
				return;

			typename std::basic_string<CharT, Traits, Alloc>::size_type p = 0;
			while ((p = str.find(target, p)) != std::basic_string<CharT, Traits, Alloc>::npos)
			{
				str.replace(p, target.size(), replacement);
				p += replacement.size();
			}
		}
	}

	/**
	 * Deleter that adds the item to the cull list, that is, queues it for
	 * deletion at the end of the current mainloop iteration
	 */
	struct cull_delete
	{
		void operator()(Cullable* item);
	};

	/**
	 * Deletes all elements in a container using operator delete
	 * @param cont The container containing the elements to delete
	 */
	template <template<typename, typename> class Cont, typename T, typename Alloc>
	inline void delete_all(const Cont<T*, Alloc>& cont)
	{
		std::for_each(cont.begin(), cont.end(), std::default_delete<T>());
	}

	/** Deletes a object and zeroes the memory location that pointed to it.
	 * @param pr A reference to the pointer that contains the object to delete.
	 */
	template<typename T>
	void delete_zero(T*& pr)
	{
		T* p = pr;
		pr = NULL;
		delete p;
	}

	/**
	 * Remove an element from a container
	 * @param cont Container to remove the element from
	 * @param val Value of the element to look for and remove
	 * @return True if the element was found and removed, false otherwise
	 */
	template <template<typename, typename> class Cont, typename T, typename Alloc>
	inline bool erase(Cont<T, Alloc>& cont, const T& val)
	{
		const typename Cont<T, Alloc>::iterator it = std::find(cont.begin(), cont.end(), val);
		if (it != cont.end())
		{
			cont.erase(it);
			return true;
		}
		return false;
	}

	/**
	 * Check if an element with the given value is in a container. Equivalent to (std::find(cont.begin(), cont.end(), val) != cont.end()).
	 * @param cont Container to find the element in
	 * @param val Value of the element to look for
	 * @return True if the element was found in the container, false otherwise
	 */
	template <template<typename, typename> class Cont, typename T, typename Alloc>
	inline bool isin(const Cont<T, Alloc>& cont, const T& val)
	{
		return (std::find(cont.begin(), cont.end(), val) != cont.end());
	}

	namespace string
	{
		/**
		 * Escape a string
		 * @param str String to escape
		 * @param out Output, must not be the same string as str
		 */
		template <char from, char to, char esc>
		inline void escape(const std::string& str, std::string& out)
		{
			for (const auto& c : str)
			{
				if (c == esc)
					out.append(2, esc);
				else
				{
					if (c == from)
					{
						out.push_back(esc);
						out.push_back(to);
					}
					else
						out.push_back(c);
				}
			}
		}

		/**
		 * Escape a string using the backslash character as the escape character
		 * @param str String to escape
		 * @param out Output, must not be the same string as str
		 */
		template <char from, char to>
		inline void escape(const std::string& str, std::string& out)
		{
			escape<from, to, '\\'>(str, out);
		}

		/**
		 * Unescape a string
		 * @param str String to unescape
		 * @param out Output, must not be the same string as str
		 * @return True if the string was unescaped, false if an invalid escape sequence is present in the input in which case out will contain a partially unescaped string
		 */
		template<char from, char to, char esc>
		inline bool unescape(const std::string& str, std::string& out)
		{
			for (std::string::const_iterator i = str.begin(); i != str.end(); ++i)
			{
				char c = *i;
				if (c == '\\')
				{
					++i;
					if (i == str.end())
						return false;

					char nextc = *i;
					if (nextc == esc)
						c = esc;
					else if (nextc != to)
						return false; // Invalid escape sequence
					else
						c = from;
				}
				out.push_back(c);
			}
			return true;
		}

		/**
		 * Unescape a string using the backslash character as the escape character
		 * @param str String to unescape
		 * @param out Output, must not be the same string as str
		 * @return True if the string was unescaped, false if an invalid escape sequence is present in the input in which case out will contain a partially unescaped string
		 */
		template <char from, char to>
		inline bool unescape(const std::string& str, std::string& out)
		{
			return unescape<from, to, '\\'>(str, out);
		}
	}

	namespace map
	{
		/** Compares two maps and returns a list of the differences.
		 * @param first The first map to compare.
		 * @param second The second map to compare.
		 * @param out The map to store the differences in.
		 */
		template<typename Key, typename Value, typename Compare, template<typename...> typename Map>
		void difference(const Map<Key, Value, Compare>& first, const Map<Key, Value, Compare>& second,
				Map<Key, std::pair<std::optional<Value>, std::optional<Value>>, Compare>& out)
		{
			auto fiter = first.cbegin();
			auto siter = second.cbegin();

			while (fiter != first.end())
			{
				if (siter == second.end())
				{
					// Store the remaining from the first.
					while (fiter != first.end())
					{
						out[fiter->first] = { fiter->second, std::nullopt };
						fiter++;
					}
					return;
				}

				if (fiter->first < siter->first)
				{
					// The key in first is not in second.
					out[fiter->first] = { fiter->second, std::nullopt };
					fiter++;
				}
				else if (siter->first < fiter->first)
				{
					// The key in second is not in first.
					out[siter->first] = { std::nullopt, siter->second };
					siter++;
				}
				else if (fiter->second != siter->second)
				{
					// The key exists in both but the value differs.
					out[fiter->first] = { fiter->second, siter->second };
					fiter++;
					siter++;
				}
				else
				{
					// The key/value is identical in both.
					fiter++;
					siter++;
				}
			}

			// Store the remaining from the second.
			while (siter != second.end())
			{
				out[siter->first] = { std::nullopt, siter->second };
				siter++;
			}
		}
	}
}
